material_base-8.x-2.x-dev/themes/material_base_mdc/templates/form/button.html.twig

{#
/**
 * @file
 * Theme override for an 'button' #type form element.
 *
 * Notice: this tempate is not defined in core yet, see
 *   https://www.drupal.org/project/drupal/issues/1671190
 *
 * Available variables:
 * - attributes: A list of HTML attributes for the button element.
 * - children: Optional additional rendered elements.
 *
 * @see template_preprocess_button()
 */
#}

{% set button_classes = [
  'mdc-button',
  'button-submit',
] %}

{% set attributes = attributes.setAttribute('data-mdc-auto-init', 'MDCRipple') %}

<button{{ attributes.addClass(button_classes) }}>
  <div class="mdc-button__ripple"></div>
  <span class="mdc-button__label">{{ attributes.value|render }}</span>
</button>{{ children }}